In recent years, liquids containing bubbles with diameters of 1 millimeter (mm) or less have been used in various fields. Also, liquids containing bubbles with diameters of 1 micrometer (μm) or less (ultrafine bubbles) have recently been gathering attention in various fields, and apparatuses for generating such liquids have been proposed.
For example, in a fine-bubble generating apparatus disclosed in Japanese Patent Application Laid-Open No. 2008-272719 (Document 1), a gas-liquid mixed fluid sent from a pump is broken up into fine bubbles by a gas swirling shearing unit and then sent to a liquid storage tank and stored. In Document 1, the liquid in the liquid storage tank is repeatedly circulated to the gas swirling shearing unit in order to increase the density of fine bubbles in the liquid (i.e., the number of fine bubbles per unit volume).
Incidentally, Document 1 describes the liquid stored in the storage tank being extracted and used in various applications. However, the fine-bubble generating apparatus of Document 1 is a batch type apparatus that can generate an amount of liquid that can be stored in the storage tank, and cannot continuously generate and supply a liquid that contains a high density of fine bubbles.